“I need ½” x 2” bolt” is what our customers will ask for. However, this is just the beginning information that we need to match the right fastener with the right application.
Bolts can be confusing, especially when we aren’t talking the same language. Below is a brief explanation of the differences between hex bolts, hex cap screws, and hex tap bolts.
Hex Tap Bolts
Tap Bolts fully threaded regardless of size. The threads on a tap bolt goes from the tip all the way to the underside of the head of the bolt. They have a weaker tensile strength but the extended threads make them more suitable for situations where hex cap screws may not function well. Tap bolts are popular because of the versatility a fully threaded fastener provides. One length of a fully threaded tap bolt can be used to replace several lengths of a standard (partially threaded) hex bolt.
Hex Cap Bolt
Hex cap screws may have a built-in shoulder (un-threaded area under the head) which increases tensile strength of the bolt. However, the threaded length of these screws may be limited and therefore, they are not suitable for all applications. A hex cap screw has tighter tolerances on the body dimensions and features a chamfered end and a washer face under the bolt head. A hex cap screw is often called a finished hex bolt.
Hex bolts have a flat end and lack the washer face under the head. They are typically manufactured using a hot-forging process. They typically are not fully threaded but are threaded based on the formula: Two Times the Diameter + 1/4”.